1,3,3,3-tetrafluoropropene has isomers, namely, a cis isomer and a trans isomer. Hereinafter, a cis isomer may be referred to as “1234Z”, and a trans isomer may be referred to as “1234E”. A mixture of a cis isomer and a trans isomer may be referred to as “1234” or “1234EZ”. In the case where it is not intended to distinguish whether the isomer is a cis isomer or a trans isomer, the isomer will be also referred to as “1234” or “1234EZ”.
1234Z has a double bond in a molecule and therefore has a very short atmospheric life time, and thus has substantially no influence on global warming or depletion of ozone layer. 1234Z has a boiling point of 9° C. and thus is useful as an intermediate for a functional substance such as a washing detergent, a flux, a coolant, a spray, a working fluid or the like and for any of various functional products.
Conventionally known methods for producing 1,3,3,3-tetrafluoropropene include a method of dehydroiodinating 1,3,3,3-tetrafluoro-1-iodopropane by use of alcoholic potassium hydroxide (R. N. Haszeldine, et al., J. Chem. Soc. 1953, 1199-1206; CA 48 5787f) and a method of dehydrofluorinating 1,1,1,3-3-pentafluoropropane (245fa) by use of potassium hydroxide in dibutylether (I. L. Knunyants, et al., Izvest. Akad. Nauk. S. S. S. R., Otdel. Khim. Nauk. 1960, 1412-18; CA 55, 349f).
Japanese Laid-Open Patent Publication No. H11-140002 discloses a method of dehydrofluorinating 1,1,1,3,3-pentafluoropropane by use of a chromium/activated carbon catalyst to produce 1,3,3,3-tetrafluoropropene, and Japanese Laid-Open Patent Publication No. 2000-63300 discloses a method of putting 1,1,1,3,3-pentafluoropropane into contact with a chromium-based catalyst to produce 1,3,3,3-tetrafluoropropene.
Meanwhile, there are methods for producing propene by use of a dehydrofluorination reaction performed on a general fluoroalkane compound in a gas phase. For example, Japanese Laid-Open Patent Publication No. H9-67281 discloses a method of putting 1,1,1,3,3,3-hexafluoropropane in a gas state into contact with an activated carbon catalyst or a chromium oxide catalyst to produce corresponding propene. U.S. Pat. No. 2,480,560 discloses a method of putting fluoroethane into contact with activated carbon to cause thermal decomposition and thus to produce propene.
Japanese Laid-Open Patent Publication No. 2008-019243 discloses a method for produce 1,3,3,3-tetrafluoropropene by dehydrofluorinating 1,1,1,3,3-pentafluoropropane in a gas phase with use of a zirconium compound-supported catalyst in which a zirconium compound is supported on a metal oxide or activated carbon.
By these methods, however, 1234 is usually obtained as a mixture of a cis isomer (1234Z) and a trans isomer (1234E). This is inconvenient when only one of the isomers is to be used.
In such a background, it has been attempted to cause mutual conversion by isomerization of fluoroalkene. Japanese PCT National Phase Laid-Open Patent Publication No. 2010-523635 discloses a method by which E-(hydrohalo)fluoroalkene, which is a trans isomer, is put into contact with a solid catalyst such as a Lewis acid catalyst, a chromia-containing catalyst, an alumina catalyst or the like and is isomerized into Z-(hydrohalo)fluoroalkene, which is a cis isomer, by a gas phase reaction by utilization of an equilibrium reaction.
International Publication No. WO2008/030443 discloses a method by which trans-1,3,3,3-tetrafluoropropene is isomerized into cis-1,3,3,3-tetrafluoropropene by use of a chromium oxide catalyst.